And next, tonight, something different. Imagine millions of people watch your life come unglued. An all-out panic attack on TV. It happened to our Dan Harris. But his journey of discovery brought back lessons for all of us about our lives, too. And he's telling us about it tonight. Reporter: Diane, this is a very personal story, as you know, because you were there when it all started. Sometimes things are holding you back from being happy. And you aren't even aware of it until life hits you over the head with a frying pan. That's what happened to me. From ABC news, this is "Good morning America." Reporter: Welcome to the most embarrassing day of my life. We're gonna go, now, to Dan Harris, who is at the newsdesk. Dan? Good morning, Charlie and Diane. Thank you. Reporter: This is me, ten years ago. And the reason this is the most embarrassing day of my life is not that it looks like I've been attacked by a blow dryer and a can of hair spry. No, it's that I'm about to freak out on national television. Health news, now. One of the world's most commonly prescribed medications may be providing a big bonus. Researchers report people who take cholesterol-lowering drugs called statins for at least five years, may also lower their risk for cancer. But it's too early to -- to prescribe statins solely for cancer production. Reporter: At this point, I realize I'm helpless. So, I bail right in the middle. That does it for news. We're going back to robin and Charlie. Thank you, Dan Harris. Some of the headlines of the morning. Reporter: Once the fear subsided, the humiliation rushed in. I knew with rock-solid certainty that I had just had a panic attack on national television. So, why would I tell you this very embarrassing story? Because that on-air meltdown was the culmination of something that had been building for years. Something I had never stopped to address. It's something we all battle with, whether we have panic attacks or not. Call it the voice in your head. I feel stress. Reporter: It's the inner narrator that can control us and get in the way of living the life we want to lead. For Brian Simmons, it was outbursts of anger. I would act very reactively. Reporter: For Becky Schmitz, it was emotional eating. Eating was my security blanket. Reporter: For a young Dr. Mehmet oz, it was a racing mind that kept him from focusing on one thing at a time. For me, saying a voice in the head is too benign of an expression for what really happens. That massive cacophony that we hear, deafeningly loud. Reporter: Does it surprise you at all how much time we all spend fixating on these voices we hear? I have always been surprised how much time we spend wasted on the voices in our head telling us we are not good enough. Reporter: In my case, like many Americans, my inner voice was pushing me to succeed. This is me in my late 20s. Thank you, Dan. Reporter: I had my dream job. But I also had doubts about whether I was good enough. It's hard to do that. I'm going to try. My solution, become a workaholic. After 9/11, I volunteered to spend years in war Zones, where I covered the heroics of our men and women overseas. And got a real taste of the horror and adrenaline of combat. After years of barreling forward, when I finally slowed down, it was as if my mind revolted and I got depressed. And so, in my free time, I briefly but stupidly began self-medicating. And it was those recreational drugs, my doctor would later tell me, that almost certainly produced that on-air panic attack. But losing it in front of 5 million people became a turning point. It set me off on a strange, unplanned odyssey. The kind of search so many of us embark on for answers, understanding and strength. Ultimately, it would lead me to something I never would have expected, as it has for Dr. Oz and millions of others. Going inside my mind is no longer going behind enemy lines. Reporter: After a journey that involved megachurches, self-help gurus, what I found is simple, and completely free. It's done by executives, proathletes and U.S. Marines. It's not a miracle cure. But it will make you about 10% happier. More on that right here tomorrow night. And for all of us who have been through this with you, wow. Thank you. Thank you. Thank you. And learn about the simple answers Dan found tomorrow on "World news," and his new book "10% happier."

This transcript has been automatically generated and may not be 100% accurate.

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